CAMP PENDLETON  Waves of amphibious assault vehicles crashed onto the beach Monday at Camp Pendleton, launching the 1st Marine Division back to the Corps’ seafaring roots and ahead to its peacetime future.

About 10,000 of the division’s 23,000 Marines and sailors have been participating in Steel Knight, a three-week exercise that ends Dec. 18.

As deployments to Afghanistan wind down, the Corps is preparing its forces for a more diverse range of operations projected from ships at sea, from humanitarian assistance to conventional warfare. It’s part of the U.S. shift of military personnel and resources toward the Pacific.

Last year a landlocked round of Steel Knight involving fewer troops focused on counterinsurgency, the main thrust for the military during the last 11-plus years of combat.

This year, the training event was revamped and expanded to include a sunrise assault on Red Beach as well as live-fire exercises at the Twentynine Palms Marine base.

“Many of the Marines have never been involved in amphibious operations. So we have to start from ground zero in making sure those young Marines who are very good at counterinsurgency now upgrade their skill set,” said Maj. Gen. Ronald Bailey, commanding general of the 1st Marine Division headquartered at Camp Pendleton.

Counterinsurgency isn’t going away, Bailey added. “It’s absolutely important and critical to maintain that skill set,” he said. “But as you know the president has turned our focus to Asia and the Pacific.”

That region is of strategic importance to the United States, a global maritime nation that moves 90 percent of its commerce by sea, he said. “Amphibious operations are “a skill that our Marines must understand in terms of how it is organized, how the waves come in, how we conduct assaults and the different types of amphibious operations.”

In a parallel exercise called Valiant Mark, an infantry battalion from Singapore stormed the beach alongside the American Marines and sailors.

The effort to seize Red Beach began Saturday night, when reconnaissance Marines landed to assess conditions such as the number of enemy forces and whether the soil and other aspects of the terrain were suitable for an amphibious landing.

“They’re already here, you just can’t see them, which is good,” Col. Scott Wertz, the division’s director of operations and training, said Monday morning.

A company of amphibious assault vehicles clattered onto the beach just before 7 a.m., carrying an infantry battalion in their steel seafaring bellies. As the sun rose over the bluff, the vehicles spread out across the beach. The ramps fell, and out popped infantrymen with rifles drawn.

According to the scenario, there weren’t many enemy fighters around to shoot at. The Corps trains to avoid beaches dug in with large numbers of enemy troops, preferring to use reconnaissance or naval gunfire and airstrikes to clear the way. The idea is to race ahead to secure territory without getting bogged down in fierce battles with heavy casualties, like the one on Iwo Jima in World War II.